This is a book that needs no introduction. By this time, if you
don't know what the World Wide Web is, then you probably haven't
heard of Rollerblades, VCRs, or Boris Yeltsin either.

In this chapter, we give the world's quickest introduction to Web
technology and the roles of the WebMasters who breathe life into each
Web document. If you want to learn more about the history of the Web,
or how to make your Web pages "cool," or the social impact of the Internet, or
how to make money online, etc., etc., etc., well, we include a
bibliography at the end of this chapter, and we can also recommend
many of the books sitting next to this one on the bookstore shelf.
But we don't get into those issues.

This is a book by impatient writers for impatient readers.
We're less interested in the hype of the Web than we are in what
makes it actually tick. We'll leave it to the pundits to predict the
future of the Web, or to declare today's technology already outdated.
Too much analysis makes our heads spin; we just want to get our Web
sites online.

We've organized this book in a roughly "outside-in" fashion--that is,
with the outermost layer (HTML) first, and the innermost layer (the
server itself) last. That way, the material most readers are
interested in is immediately accessible, while the material of less general
interest remains in the back. But since it's a good idea for all
readers to know how everything fits together, let's take a minute to
breeze through a description of the Web from the inside-out: no
history, no analysis, just the technology basics.

The tool that most people use on the Web is a browser,
such as Netscape Navigator, Internet Explorer, or Mosaic. Web browsers
work by connecting over the Internet to remote machines,
requesting specific documents,
and then formatting the documents
they receive for viewing on the local machine.

The language, or protocol, used for Web transactions
is Hypertext Transfer Protocol, or HTTP. (HTTP is covered in
Chapter 17, HTTP Overview through Chapter 20, Media Types and Subtypes.)
The remote machines
containing the documents run HTTP servers that wait
for requests from browsers and then return the specified document.
The browsers themselves are technically HTTP clients.

Now, let's take a short detour in this overview. One of the most
important things to grasp when working on the Web is the format for
URLs. A URL is basically an address on the Web, identifying each
document uniquely (for example,
http://www.ora.com/products.html). Since URLs are so intrinsic to the
Web, we'll discuss them here in a little
detail. The simple syntax for a URL is:

http://host/path

where:

host

is the host to connect to, for example www.ora.com or
altavista.digital.com.
(While many Web servers run on hosts beginning with www, the
www prefix is just a convention.)

path

is the document requested on that server.

Most URLs you encounter follow this simple syntax. A more generalized
syntax, however, is:

scheme://host/path/extra-path-info?query-info

where:

scheme

is the protocol used to connect to the site. For Web sites, the
scheme is http. For FTP or Gopher sites, the scheme is
(respectively)
ftp or gopher.

HTML documents also often use a "shorthand" for linking to
other documents on the same server, called a relative URL.
An example of a relative URL is images/webnut.gif. The browser knows to translate
this into complete URL syntax before sending the request.
For example, if the document with URL
http://www.ora.com/books/webnut.html contains a
reference to images/webnut.gif, the browser reconstructs
the relative URL as a full (or absolute) URL,
http://www.ora.com/books/images/webnut.gif, and requests
that document independently (if needed).

Often in this book, you'll see us refer to a URI, not a URL.
A URI (Universal Resource Identifier) is a superset of URL,
in anticipation of different resource naming conventions
being developed for the Web. For the time being, however,
the only URI syntax in practice is URL--so while purists
might complain, you can safely assume that "URI" is synonymous
with "URL" and not go wrong (yet).

While Web documents can conceivably be in any format, the one that
has been adopted as the standard is Hypertext Markup
Language (HTML), a language
for creating formatted text interspersed with images, sounds,
animation, and hypertext links to other documents anywhere
on the Web. Chapter 2, HTML Overview through Chapter 8, Browser Comparison,
cover the most current version of HTML.

When static documents aren't sufficient for a Web site's needs, it uses tools such as CGI, Java, and JavaScript. CGI is a way
for the Web server to call external programs instead of simply
returning a static document.
Chapter 9, CGI Overview through Chapter 16, Other CGI Resources, are for CGI programmers.
Java is an object-oriented language for writing all sorts
of programs that can be downloaded over the Web,
from animations to spreadsheets. This book does not cover
the complexities of Java, but it does cover JavaScript, a related
language that can be written directly into the HTML
document. (For details on Java, we recommend Java in a Nutshell, by
David Flanagan.)